1. Field of the Invention
The present invention relates to a water base ink set for ink-jet recording to be used for an ink-jet recording apparatus.
2. Description of the Related Art
In the ink-jet recording system, ink droplets are formed, for example, by means of the electrostatic attraction system, the system in which mechanical vibration or displacement is applied to the ink by using a piezoelectric element, and the system in which bubbles are generated by heating the ink to utilize the pressure generated thereby. All or a part of the ink droplets are adhered to a recording objective material such as paper to perform the recording.
The ink-jet recording system is advantageous in that the high printing or typing quality and the high print or photographic quality are obtained by controlling the discharge of the minute liquid droplets. Colors approximate to those obtained by the full color system can be reproduced and images without involving any granular texture can be formed by allowing the minute ink droplets of several picoliters to land highly accurately on the paper surface. However, in order to make it possible to discharge the minute liquid droplets as described above, it is necessary to establish a highly accurate landing control technique while using the sufficiently thin discharge nozzle. In order to highly accurately discharge the ink from the discharge nozzles having minute diameters as described above, it is necessary to remove the dust and impurities from the ink. Therefore, it is necessary that the precise filtration or microfiltration is performed for the ink for ink-jet recording, and materials, which are sufficiently washed, are used for all parts which make contact with the ink.
Most of general full color ink-jet printers, which are based on the use of an ink set of four colors of black, yellow, magenta, and cyan, use water base inks containing acid dyes in view of the toxicity and the coloring performance on the paper. However, the vividness is insufficient in some cases depending on the color. It is demanded to obtain a vivid image like those depicted with marker pens. Such a demand is especially great for the yellow. In order to satisfy the demand as described above, it is preferable that a basic dye, which develops a vivid color, is used as actually used for the marker pen. However, if water base inks, which contain basic dyes, are used for the water base inks of all colors to be used for the full color ink-jet printer, a resultant ink set is hardly considered to be appropriate in view of the color balance, even though the respective single colors are vivid.
On the other hand, Japanese Patent Application Laid-open No. 7-314880, which relates to an ink-jet recording material having an ink-receiving layer provided on a support, describes a method in which a basic dye is contained in the ink-receiving layer, and an ink for ink-jet recording containing an acid dye having a hue or tone different from that of the basic dye is used to perform the recording, and a method in which an acid dye is contained in the ink-receiving layer, and an ink for ink-jet recording containing a basic dye having a hue or tone different from that of the acid dye is used to perform the recording. However, in the methods as described above, it is necessary to use the ink-jet recording material which is allowed to contain the dye. Further, the inks of all colors are unbalanced to the use of the acid dyes or the basic dyes. The methods as described above are hardly considered to be appropriate in view of the color balance as well.
Therefore, when it is intended to obtain a vivid image having good color balance, it is preferable to use a water base ink containing an acid dye and a water base ink containing a basic dye in combination. However, in such a case, it is feared that the water base ink containing the acid dye and the water base ink containing the basic dye are mixed with each other at a head discharge section of an ink-jet printer to produce any deposit. The degree of the production of the deposit differs depending on, for example, the type of the dye, the concentration of the dye, the type of the solvent, and the concentration of the solvent. However, when the deposit is produced, then the clog-up arises at the head discharge section in some cases, and it is impossible to highly accurately control the discharge and the landing in other cases.
The acid dye and the basic dye are dissociated into cations and anions in the aqueous solution. It is considered that the deposit is produced as follows when the both dye solutions are mixed with each other. That is, the anion contained in the acid dye and the cation contained in the basic dye are attracted to one another, and the fundamental moieties of the dyes are bonded to one another. Therefore, if the anion contained in the acid dye and the cation contained in the basic dye are prevented from being attracted to one another, it is possible to avoid the production of the deposit. However, in general, the anion and the cation tend to effect the attraction. Therefore, it is difficult to avoid the production of the deposit when the both inks are mixed with each other.